This invention relates to selective call receivers, such as pagers, for operating in the communication environment of frame based synchronous selective call systems. In particular, this invention relates to, but is not necessarily limited by, a multichannel selective call receiver and a method for channel monitoring therein.
Multichannel selective call receivers, such as multichannel pagers, operating in the communication environment of synchronous selective call systems are known. Within the communication environment, selective call signals are received and processed by the multichannel selective call receivers to obtain information for users.
Conventionally, a cyclical frame based synchronous selective call system operates with a messaging protocol that specifies how information is encoded as frames onto radio frequency (rf) carriers or channels to form selective call signals. Typically, the messaging protocol also provides signal parameters for specifying which frames of a selective call signal have to be processed to obtain the information. These signal parameters can be encoded within the selective call signal or stored within a selective call receiver.
Frames specified for processing, henceforth referred to as selected frames, can be far apart from each other or closely spaced together within a selective call signal. In processing these selected frames, a selective call receiver can also check the quality of the selective call signal. For example, this quality can be checked by counting the selected frames detected over a period of time. By comparing a control setting with the number of selected frames detected, the selective call receiver can then determine whether to continue monitoring the channel to receive the selective call signal or to scan for other channels to monitor for selective call signals.
In most situations, detection of selected frames enables a selective call receiver to effectively determine whether a channel should still be monitored. However, problems can arise in some situations when fixed control settings are compared with selected frames that can vary in number for different selective call signals or for different selective call systems. For example, a small fixed control setting requires only a small number of selected frames for comparing. Such a small number may, however, be insufficient to reliably determine whether to continue monitoring the channel especially when the selected frames are closely spaced within a selective call signal. On the other hand, a large fixed control setting requires a long period of time to detect a sufficient number of selected frames that are spread far apart within a selective call signal. However, monitoring a channel over such a long period of time without receiving information is not efficient especially when the selective call receiver is powered by limited content batteries. Furthermore, even though a channel that is monitored does not have any information, other channels may be present in the communication environment to provide such information.
It is an object of this invention to provide a multichannel selective call receiver and a method for channel monitoring therein.
According to one aspect of the invention, there is provided a multichannel selective call receiver for operating within a cyclical frame based synchronous selective call system, said multichannel selective call receiver comprising:
a signal monitor for monitoring a channel to receive a selective call signal;
a signal processor for processing selected frames of said selective call signal, said selected frames occurring cyclically and regularly spaced between non-selected frames; and
a controller coupled to said signal monitor and said signal processor,
wherein, in response to a comparison of at least one predetermined number with a signal parameter indicative of number of said selected frames in a cycle, said controller is adapted to control said signal monitor and said signal processor to receive and to process one or more of said non-selected frames in addition to said selected frames to thereby determine whether to stop or to continue monitoring said channel.
Preferably, said controller can be further adapted to control said signal processor to detect each of said selected frames.
Suitably, said controller can be further adapted to count undetected ones of said selected frames.
Preferably, said controller can be further adapted to compare number of said undetected ones with a threshold count, said threshold count being based upon said signal parameter.
Suitably, said controller can be further adapted to control said signal monitor to monitor at least one other channel for selective call signals when said number of said undetected ones is greater than said threshold count.
Preferably, said controller can be further adapted to control said signal monitor to scan for said other channel.
Suitably, said controller can be further adapted to select said other channel from a memory within said multichannel selective call receiver.
Preferably, said controller can be further adapted to determine said signal parameter.
Suitably, said controller can be further adapted to schedule said one or more of said non-selected frames for processing when said signal parameter is greater than said predetermined number.
Preferably, said controller can be further adapted to select mandatory frames as said one or more of said non-selected frames.
Suitably, said signal monitor can comprise a receiver.
Preferably, said signal processor can comprise a demodulator.
Suitably, said signal processor can comprise a decoder.
According to another aspect of the invention, there is provided a method for channel monitoring by a multichannel selective call receiver operating within a cyclical frame based synchronous selective call system, said method comprising the steps of:
monitoring a channel to receive a selective call signal;
processing selected frames of said selective call signal, said selected frames occurring cyclically and regularly spaced between non-selected frames; and
controlling, in response to comparing at least one predetermined number with a signal parameter indicative of number of said selected frames in a cycle, said steps of monitoring and processing to receive and to process one or more of said non-selected frames in addition to said selected frames to thereby determine whether to stop or to continue monitoring said channel.
Preferably, said step of processing can comprise the step of detecting each of said selected frames.
Suitably, said step of processing can further comprise the step of counting undetected ones of said selected frames.
Preferably, said step of processing can further comprise the step of comparing number of said undetected ones with a threshold count, said threshold count being based upon said signal parameter.
Suitably, said step of controlling can comprise the step of monitoring at least one other channel for selective call signals when said number of said undetected ones is greater than said threshold count.
Preferably, said step of monitoring can comprise the step of scanning for said other channel.
Suitably, said step of monitoring can comprise the step of selecting said other channel from a memory within said multichannel selective call receiver.
Preferably, said step of processing can comprise the step of determining said signal parameter.
Suitably, said step of controlling can comprise the step of scheduling said one or more of said non-selected frames for processing when said signal parameter is greater than said predetermined number.
Preferably, said step of scheduling can comprise the step of selecting mandatory frames as said one or more of said non-selected frames.
Suitably, said method can further comprise the step of waiting for a next frame to process.